Tuning Fork Keeps This Throwback Digital Clock Ticking

Whatever kind of clock you’re interested in building, you’re going to need to build an oscillator of some sort. Whether it be a pendulum, a balance wheel, or the atomic transitions of cesium or rubidium, something needs to go back and forth in a predictable way to form the timebase of the clock. And while it might not make the best timepiece in the world, a tuning fork certainly fits the bill and makes for a pretty interesting clock build.

One of the nice things about this build is that [Kris Slyka] got their inspiration from a tuning fork clock that we covered a while back — we love it when someone takes a cool concept and makes it their own. While both clocks use a 440 Hz tuning fork — that’s an A above middle C for the musically inclined — [Kris] changed up the excitation method for their build. She used a pair of off-the-shelf inductors, placed near the ends of each arm and bridged by a strong neodymium magnet to both sense the 440-Hz vibrations and to provide the kick needed to keep the fork vibrating.

As for the aesthetic of the build, we think [Kris] really nailed it. Using through-hole components, old-school seven-segment displays, and a home-etched PCB, she was able to capture a retro look that really works. The RS-232 port and the bell jar enclosure complete the feel, although we’re not sure about the custom character set [Kris] designed — it’s cool and all, but makes it hard for anyone else to read without a little practice. Regardless, this is a fun build, and we’d imagine the continuous tone coming from the clock is pretty pleasing.

37 thoughts on “Tuning Fork Keeps This Throwback Digital Clock Ticking

  1. So will the next revision be inside a “double wall borosilicate glass coffee mug” covered on the open end with a cap/base of thermablok aerogel insulation or even just expanded polystyrene. Add a few heating resistors and a thermometer to keep the internal temperature constant over a day, to prevent the loss/gain of seconds over a day.

    A temperature controlled tuning fork!

      1. Yea, but you could drop the power required by at least an order of magnitude or maybe two, by using any of the cheap vacuum “double wall borosilicate glass” container that are sold as glasses to keep drinks cold or hot.

        1. Before that, they used a complex mechanical arangement of bars of different metals to try to counteract the thermal properties of the other metals–resulting in a temperature stable pendulum.

        1. You don’t need to be perfect. Just better than the cheapest quartz clock without any temperature compensation. Standard “good” crystals get 10 ppm over -40 to +85 which means a maximum deviation of 25 seconds over a month. In practice, the clock will not see temperature variations greater than 10 C and a quartz clock will not lose or gain more than 2 seconds a month.

    1. I was curious why that was, so I watched the video. Turns out the designer was going for a ‘found device’ type of junk asthetic. That, like the choice of jibberish font make me question wether this is a hack or just a misplaced art project. Honestly, watching the video past where the designer explains how the tuning fork circuit works was a mistake.

      I’m tempted to build the tuning fork part of the design and maybe make a clock as well. I’d prefer to use an ESP8266 and use NTP to track the drift of the tuning fork. Might be nice to have a frequency tuning kind of partial dial display to show the current frequency error. Maybe log the temp and error to a server and figure out the behavior of the fork long term. MIght need a pressure and humidity sensor as well to determine what contribution those factors have to any frequency error.

      1. >make me question wether this is a hack or just a misplaced art project

        What’s the difference? They are hardly mutually exclusive. For that matter, what’s your issue with art anyways?

        Art using electronics and mechatronics as it’s medium of creation is literally what started the modern maker movement (Processing, and it’s child Arduino, were originally designed to let artists utilize microcontrollers in sculpture) and is one of the biggest sources of innovation and boundary pushing in hobby electronics.

        The arts and crafts are the source of a ton of hacks. You don’t think that woodworkers, sculpters, and jewelry-makers don’t regularly have the exact same issues with tools and materials that we do? Innovations in those arts regularly end up contributing to materials science and materials processing that benefit makers, scientists, and engineers the world over.

        Likewise, it is often artists who seek to push the boundaries on things like 3d printing, which leads to innovation in the space. Heck, a lot of the tools we often use for hobby electronics are stolen straight from a jewelers toolbox.

        As makers we are forced to be both engineers AND artists, not just one or the other, and we benefit from having the skills, tools, and innovations of both.

        1. A hack is an expedient solution to an issue in a case where a better solution is not possible because of some constraint like cost, time, availability, expertise… etc.

          An art project is not a hack because it is done exactly for the point of itself. Not because you couldn’t do better this time around.

          1. This is what I meant. A hack is a repurposing of one thing for an unintended use generally as an expedient when a better solution is not available. This is an art project pretending to be a hack. They designed it to *look* like it was something repurposed as a different thing.

            It’s interesting as an art piece, but it’s less interesting to *hack a day* becaue it’s not a hack.

        2. You have to remember what you mean by “art”.

          Art is a piece of bailing wire wrapped around a hose because of the aesthetics and the message it delivers.

          A hack is a piece of bailing wire wrapped around a hose because you didn’t have a proper hose clamp in your toolbox.

      2. I kind of figured questions like this would have come up. Obviously the guy just wanted to experiment with this. If all you are looking for is a clock, you would just go with the cheap quartz units. It is the same as people that still like the mechanics of a fine watch even though it is not going to keep time as well as the $10 quartz watch at the discount store. It is the “art” and science of mechanical time keeping. In this case, its a hybrid of electronic and mechanical devices. A bit like a steam powered Corvette.

  2. Very cool. Obvious choice works be to use C and divide with a binary counter. We’ve been chatting about this in freenodes ##arduino

    Some want to try using the fork as the microcontrollers clock…

    Fun fun fun

          1. If you use the French standard A435 instead of A440, your C6 will be 1034.6 Hz. If you were using a baroque pitch, that would be A415.

            A classical pitch between 427–430 Hz would result in C6 of 1015 – 1023 Hz, so you could have a classical pitch tuning fork and file a little bit off the ends to get exactly 1024 Hz.

  3. cool project! I thought: How peculiar, someone using BC547 Transistors … like we use in some German electronics beginners books and experiment kits. And then I see the “Ebelin Nagellackentferner” (nailpolish remover from a German drugstore chain). :) Apparently some transistors have a sort of “nationality”. Amusing!

    1. When I moved to Canada I had to trade in my BC109s for 2N2222s at immigration control ;-)

      Does ZTX212 have a nationality? I swear it got suddenly popular early 90s then dropped out of sight again.

    2. I know exactly what you mean! I’m a bit of a tool nerd myself and can (most of the time) tell where the video was shot just looking at the tools :)

      In this video the first hint was the cutting mat, got the same… And the pencils. The 2mm Faber Castell TK 9400 Fallminenstift (clutch pencil) is a great tool!

  4. Around this pitch and it’s octaves the length unit of a foot comes about in powers of 2, this is a 1000 years old or more in organ terminology.

    If you use 432Hz you can have eternal time and be in harmony with the universe. Thin conformable aluminum headgear required.

    Video reminds me of those puppet shows on live TV in the 1950’s, sans socks.

  5. As a watchmaker, I always hated quartz watches but I recently found a mint Bulova fork watch with original pricetag in a gift bag full of crappy quartz watches, and tuning fork watches are cool as hell to me.

    This clock is beautiful and well done!

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